There seems to be a bug that Google is working on where some searchers are getting left in the dark. Well, stuck in Google's dark mode or dark theme setting and unable to go back to light theme. Google's community manager, Minhaj K., said it is investigating the reports of this issue.
There are numerous complaints in this Google Web Search Help thread of this, and you can see in the screenshot below (the one above I made, I thought I was being cute) that the setting shows "light theme" selected but clearly the interface is stuck in dark theme:
Minhaj K. from Google said "Thank you for reporting this issue. We're investigating the problem and appreciate your patience as we work to resolve it as quickly as we can."
That was several days ago, I am not sure if it is fixed, I have not heard back yet from Google.
Forum discussion at Google Web Search Help.